This invention relates to a speed change control device for shifting a main speed change mechanism and an auxiliary speed change mechanism which are disposed within a vehicle housing of a tractor.
There is well known from, for example, U.S. Pat. No. 5,269,195 (which corresponds to JP, U No. 5-35527) a speed change control device in which control shafts for shifting respectively a main speed change mechanism and an auxiliary speed change mechanism for a tractor are slidably and rotatably supported within a vehicle housing in a direction across the housing so as to extend outwardly of the vehicle housing and are connected respectively to a main change lever and to an auxiliary change lever such that each of the control shafts is selectively displaced slidingly and rotationally by a selective pivotal operation of each change lever.
According to the prior art, the control shaft for shifting the main speed change mechanism extends outwardly to one side of the vehicle housing and is connected to the main change lever disposed at one side of the housing whereas the control shaft for shifting the auxiliary speed change mechanism extends outwardly to the other side of the vehicle housing and is connected to the auxiliary change lever disposed at the other side of the housing. Thus, the change levers, control shafts and connecting members therebetween are arranged at one and the other sides of the vehicle housing so that an operator is hindered from riding on and getting off a seat on the vehicle housing. Further, a support member for supporting the main change lever and another support member for supporting the auxiliary change lever are separately provided, so that costs for manufacturing and assembling such support members are increased so much.
Accordingly, a main object of the present invention is to provide a novel speed change control device in which main and auxiliary change levers are disposed only at one side of a vehicle housing such that a support member for both of the change levers is made common, whereby the drawbacks of the speed change control device according to the prior art are eliminated.
The present invention relates to a speed change control device for a tractor having a main speed change mechanism (26) and an auxiliary speed change mechanism (29) which are disposed in a vehicle housing (2). The speed change control device according to the present invention is characterized in:
that a slidable and rotatable first control shaft (61) for shifting the main speed change mechanism (26) and a slidable and rotatable second control shaft (67) for shifting the auxiliary speed change mechanism (29) are arranged such that the first and second control shafts extend laterally within the vehicle housing (2) and project outwardly to one side of the vehicle housing; and
that a support member (70) for pivotally supporting a main change lever (74) and an auxiliary change lever (75) is fixedly provided at one side of the vehicle housing (2), the first and second control shafts (61, 67) being connected respectively to the main and auxiliary change levers such that each of the first and second control shafts is selectively displaced slidingly and rotationally by a selective pivotal operation of each of the main and auxiliary change levers.
Because the first control shaft (61) for shifting the main speed change mechanism and the second control shaft (67) for shifting the auxiliary speed change mechanism project outwardly to one side of the vehicle housing (2) and are connected respectively to the main change lever (74) and auxiliary change lever (75) which are pivotally supported by a common support member (70) fixedly provided at one side of the vehicle housing, both of the main and auxiliary chane levers are disposed only at one side of the vehicle housing. Thus, there exists no change lever at the other side of vehicle housing so that an operator is not hindered from riding on and getting off a seat by any one of the change levers. Because the support member (70) is made common to both of the change levers, costs for manufacting and securing the same are greatly reduced as compared to the prior art structure.
For avoiding an error in operating the change levers, it is preferred that the main change lever (74) and the auxiliary change lever (75) are disposed at one side of a seat (76) on the vehicle housing (2) such that the main change lever is located outwardly of the auxiliary change lever and such that a grip portion (74a) of the main change lever is located at a higher level than a grip portion (75a) of the auxiliary change lever. Speed change operation of the main speed change mechanism is constantly made during the running of vehicle, whereas the auxiliary speed change mechanism is usually used such that a suitable change ratio thereof is preset prior to the running of vehicle in response to the running condition. According to the above-referenced arrangement of change levers, the main change lever, which is constantly operated during the running of vehicle, is disposed at a location where an operator on the seat can operate the lever easily, whereas the auxiliary change lever, which is seldom operated during the running of vehicle, is disposed at a location where the operator is hard to operate the lever. Thus, an error in operating the change levers is seldom caused.
For a dust- and water-proof purpose, it is preferred that the support member is composed of a cover member (70) which surrounds the first and second control shafts (61, 67), lower portions of the main and auxiliary change levers (74, 75) and connecting members (80, 87) between the first and second control shafts and the main and auxiliary change levers. An opening (70b) is formed in the cover member for assembling the connecting members and is closed by a closure member (70c) secured to the cover member. The cover member achieves a dust- and water proof structure at a low cost. Additionally, grease may be coated between the change levers and control shafts for enhancing lubrication therebetween.